Pill-resistant yarns



United States Patent M 3,279,163 PILL-RESISTANT YARNS Arthur Lulay, Wilmington, Del., and John Turner Lund, Kinston, N.C., assignors to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Filed Jan. 6, 1964, Ser. No. 336,056

3 Claims. (Cl. 57-140) This invention relates to textile yarns and fabrics and particularly to yarns containing a blend of bicomponent fibers and homofibers. It is more particularly concerned with yarns which when knitted into fabrics Will not pill to an objectionable degree during wearing.

Synthetic fibers, because of their greater strength and good crimp have always been subject to more or less severe pilling. Pilling is the term used to describe the small balls of fibers which form on the surface of some fabrics as a result of abrasion during wear. Filling is especially severe in loosely constructed, high bulk fabrics, such as knitted sweaters. The bicomponent fibers with their very high crimp index are especially prone to pilling. Pilling can be minimized by the use of high twist in the yarns but this destroys the bulk and aesthetics of the fabrics.

Other efforts have been made to overcome pilling and some success has been obtained with polyamide fibers by highly local degradation of the fiber by treatment with hydrogen peroxide as taught by US. Patent 3,050,822 to Matray and Stine. But this treatment is not effective for fibers spun from polymers or copolymers of acrylonitrile.

Fibers of lower tenacity can be spun from solutions of acrylonitrile polymers of low molecular weight as indicated by a low inherent viscosity, but this has yielded fibers of poor quality, and spinning has been difficult.

The tenacity of fibers of acrylonitrile can also be controlled somewhat by varying the degree of drawing or stretching of the fibers after spinning. A low draw-ratio yields fibers of lower tenacity. But, thus far, it has been difficult to obtain fibers which are sufiiciently Weak to avoid pilling and yet sufficiently strong to knit satisfactorily.

One solution to the problem has been the use of a blend of a high-shrinkage bicomponent fiber and a low tenacity, low shrinkage and low-crimp homofiber. When the yarn made from this blend, or the resulting fabric, is boiled off, the bicomponent fiber shrinks and crimps and tends to migrate to the core of the yarn leaving the weak and straight fiber on the surface. Due to lack of crimp the surface fibers have little tendency to become entangled to form pills and the low tenacity of the fibers further contributes to pill resistance. This means of overcoming pilling leaves the high crimp bulky fibers in the core of the yarn and thus some of the potential aesthetic qualities of the fibers are lost. Another shortcoming of .knit fabrics made from these particular yarns is that such fabrics in the form of garments, especially sweaters, will shrink excessively when piece dyed and tumble dried. Uniform dyeing of these blends is also difficult because of the different dyeing rates of the two polymers.

It is, therefore, an object of the present invention to prepare knit fabrics from fibers spun from polymers of acrylonitrile which will have the high bulk, high cover and other aesthetic qualities of bicomponent fibers but which will not pill to an objectionable degree and which can be readily union dyed to uniform shades.

These objects are accomplished by blending from about 70 to 90% of bicomponent fibers having low tenacity as a result of a low draw-ratio with from about to 30% of normally strong homofibers spun from a terpolymer of acrylonitrile, an alkyl vinyl pyridine and methyl acry- 3,279,163 Patented Oct. 18, 1966 late. Yarns from these blends have ample strength to give good knittability, have the good bulk and the fine aesthetics of the bicomponent fibers, and fabrics knit from these yarns have good resistance to pilling and can be readily dyed to uniform shades.

The bicomponent fibers of this invention are spun from two different polymers in a side-by-side relation along the length of the fiber. One of the polymers is acrylonitrile and the other a copolymer of acrylonitrile and sodium styrenesulfonate. The difference in shrinkage of the two sides of the fiber accounts for the high crimp potential. The content of from 1 to 4% by weight of copolymerized sodium styrenesulfonate gives the fiber affinity for basic dyes. This bicomponent fiber is drawn only 1.8x to 2.1x and is, therefore, a low-tenacity fiber.

The homofiber of this invention is a terpolymer of acrylonitrile, an alkyl vinyl pyridine, and an alkyl acrylate. Preferably the terpolymer contains at least acrylonitrile, from 2 to 10% of the vinyl pyridine and from 4 to 13% of the alkyl acrylate. After being extruded the fiber is drawn from about 3 to 6 and preferably about 4.5 X. The alkyl vinyl pyridine content of the fiber imparts afiinity for acid dyes. It is possible, therefore, to union dye fabrics made from these blended fibers by using both acid and basic dyes successively in the same bath. It is possible also to dye only one of the fibers if desired to yield a heather-like effect, or to dye the two kinds of fibers different colors for various twotone effects.

The homofiber adds strength to the blend, and the yarns spun from blends will knit satisfactorily. Knittability of a yarn is determined as follows:

The yarn is knit for 15 minutes on a Zl-gauge fullfashioned knitting machine under conditions to give a loose stitch construction. This makes the test very severe since loose constructions are more difficult to knit. Two control yarns are similarly knit for 15 minutes each, one being a good yarn known to knit satisfactorily in commercial operation and the other known to be unsatisfactory. The number of holes in fabric from each yarn is counted. The machine is set with a very loose stitch such that the good yarn gives 0 to 25 holes during the 15 minute run, and the poor control yarn gives 40 to holes. This is usually about 11 courses per inch. If the number of holes in the test item is equal to or less than those of the good control, the yarn is rated acceptable. If the number of holes is equal to or greater than the number of holes for the poor control, the test item is unacceptable. If the number of holes is between the numbers for the good and poor controls, then the test item is border-line in knittability.

The present invention will be further illustrated by the following examples in which parts and percentages are by Weight.

Example I A tow of bicomponentfiber is spun from two following polymer compositions using the spinning apparatus and method of US. Patent 3,038,236:

Polymer I-A polymer blend of 90% polyacrylonitrile and 10% of a copolymer of 96% acrylonitrile and 4% sodium styrenesulfonate Polymer IICopolymer of 96% a'crylonitrile/ 4% sodium styrenesulfonate For spinning, each polymer is dissolved separately in dimethyl formamide and the two solutions brought together at the spinneret hole to yield filaments with the polymers in a side by side relation along the length of the fiber. After spinning, the fibers are Washed in hot water and stretched (drawn) to 180% (1.8x) of the spun length. The tow is then dried at C. The individual filament denier is 3.5 (.38 tex.) and the total denier of the tow 3 620,000 (68,200 tex.). The fibers have a shrinkage of 4.0% when boiled off and dried. This will be referred to as Fiber A.

A homofiber is spun from a terpolymer of 89.6% acrylonitrile, 5.7% methyl acrylate, and 4.7% 2-methyl-5-vinyl pyridine. After washing in hot water, this fiber is drawn to 450% of its spun length (4.5x After drying, it has a denier per filament of 3.0 (.33 tex.) and a total tow denier of 470,000 (51,700 tex.). The shrinkage of this fiber is 2.5%. This will be referred to as Fiber B.

Three tows of Fiber A and one tow of Fiber B are combined and processed through a Pacific converter using a 3.5 inch (8.89 cm.) cutter roll to give a sliver with cut length varying from 2.5 to 4.5 inches (6.35 to 11.43 cm.). The ratio of Fiber A (bicomponent) to Fiber B (homofiber) is 80/20. Slivers of this blend are then pin drafted with 12, 15, 15, 22 and 22 pins per inch (2.54 cm.) in successive draftings. Sliver weights after each drafting are 300, 230, 150, 100 and 70 grains per yard (21, 16, 11 and 7 grams per meter) respectively. The draft increases from X on the first pass to 9x for the final pass. The final sliver is next passed through a slubber and converted to a hank roving of one and one-half 840 yard hanks per pound (395 tex.) with a twist of 0.5 Z turns per inch (t.p.i.). The drafting in the slubber is 8 The hank roving is spun to a 1/ 30 worsted count (29.6 tex.) yarn with a twist of 11 Z t.p.i. This yarn is waxed and coned and two ends of yarn are plied to give a 2/ 30s worsted count (59.2 tex.) yarn with a twist of 4.7 S t.p.i. (1.9 S turns per cm.). Upon scouring and tumble drying, this yarn shrinks 19%.

The unscoured yarn is used to knit sweaters on a 21 gauge full fashioned knitting machine at 13 courses per inch (5.2 courses per cm.).

These sweaters are dyed by placing in a nylon mesh bag and placing in a paddle wheel dyer. Before dyeing, they are scoured for 30 minutes at 71 C. in a bath containing 1.0% of a non-ionic detergent and 0.5% acetic acid, both percentages based on the weight of the sweaters.

After rinsing, the sweaters are treated in a bath of the following composition at 50 C.:

Percent Leveling salt 0.8 Glaubers salt 8.0 Sulfuric acid 3.0 Acid Blue 25 (Color Index 62055) 0.8 Acid Yellow 17 (Color Index 18965) 1.36

The temperature is raised 1.7 C. per minute until it reaches 85 C., then there is added:

Percent Cationic retarding agent (Du Pont Retarder LAN) 1.0

Basacryl Blue GL 0.48

Basic Yellow 11 (Color Index 48053) 0.9

The bath is continued at 85 C. for ten minutes then raised to the boil at the rate 0.5 C. per minute. It is held at the boil for two hours then cooled slowly to 71 C. and finally rinsed thoroughly.

An examination of the dyed sweaters reveals that the shade is uniform. The acid dyes dye the homofibers and the basic or cationic dyes dye the bicomponent fiber to the same shade of green.

In the 15-minute knittability test described above it is noted that with this yarn 20 holes appear in the knit fabric compared to 23 with the control yarn known to knit satis factorily in commercial knitting, and 75 holes for the control yarn known to be unsatisfactory for commercial knitting. It is, therefore, concluded that this yarn is satisfactory for knittability.

The tendency of the sweaters to pill is determined by actual wearing of the sweaters and also by the Random Tumble Pill Test described in ASTM D1375 (ASTM Standards, 1959 Supplement, part 10, page 173). The

rating for severity of pilling after tumbling for 5, 10, 20 and 30 minutes are as follows:

Minutes:

These values are well above the minimum acceptable value which is about 3.0. The more reliable wear test also reveals that the sweaters do not pill to a serious extent.

The final count of the stitches in the sweater is 25 courses and 18 wales per inch (10 courses and 7 wales per cm.).

Thus, the blended fibers of this invention are found to yield yarns which have satisfactory knittability, give knit fabrics which can be piece dyed to uniform shades, and have satisfactory pill resistance.

Example II A tow of Fiber A of Example I is cut into staple fiber of cut length from 2.5 to 4.5 inches (6.35 to 11.43 cm.). Likewise a tow of Fiber B of Example I is cut into staple of 2.5 to 4.5 inches (6.35 to 11.43 cm.).

Twenty pounds (9072 grams) of Fiber A staple and 5 pounds (2268 grams) of Fiber B staple are blended on the wool blender. The blended staple is then carded on the worsted card to yield a sliver of 130 grains per yard (9 grams per meter) weight. This card sliver is converted to a 2/30s yard (59.2 tex.) having a 11.0 Z (4.5 turns per cm.) twist in the singles and 4.7 S (1.8 turns per cm.) twist in the ply. This yarn is used for knitting as in Example I. There are only one tenth as many holes in the knit fabric as are observed in a fabric knit from 100% Fiber A. The knitted fabric is satisfactorily resistant to pilling. The fabric is dyed by the procedure of Example I using the following combination of dyes:

Percent Acid Red 113 0.48 Basic Red 14 0.24 Basic Red 18 0.12

A uniform red shade is obtained in this dyeing.

Example III Four ends of tow of Fiber A of Example I are con verted to sliver of 2.5 to 4.5 inch (6.35 to 11.43 cm.) length on the Pacific converter. One end of Fiber B of Example I is drawn and broken on the Turbo stapler at a plate temperature of 132 C. a stretch of 1.58 a breaker draft of 1.55 and at a rate of 140 pounds per hour (17.6 grams per second). This sliver is not heat-set and hence has a shrinkage of about 25%. It is next passed through a Hood doubler to break the filaments to lengths of 1.5 to 3.5 inches (3.8 to 8.9 cm.).

Slivers of Fiber A and of Fiber B as thus prepared are combined in a ratio of parts by Weight of Fiber A and 20 parts Fiber B and drafted on pin drafters as in Example I. The final sliver is converted to yarn and knit into full fashioned sweaters as in Example I. Knittability of this yarn is five-fold better than yarn spun from Fiber A. Pilling of the fabric is satisfactory.

Example IV A sliver made from a blend as in Example III but having 75% Fiber A of 4.5 denier and 25% Fiber B is drafted on pin drafters in successive steps to sliver weights of 400, 160, and 65 grains per yard (28, ll, 8 and 5 grams per meter). The final sliver is converted to a hank roving of 1.3, 840 yard hanks per pound (450 tex.) with a twist of 0.66 Z t.p.i. (0.26 turn per cm.). This is spun to a 1/20 worsted count (44.3 tex.) yarn with 8.3 Z t.p.i. (3.3 turns per cm.) and this is plied to 2/20s worsted count (88.6 tex.) with a ply twist of 3.5 S t.p.i. (1.4 turns per cm.). This yarn has shrinkage of 32% when boiled off.

t the pin drafter and Three different types of sweaters are knit from this yarn, one with a links-links stitch, one with a half cardigan stitch and one with a jersey stitch.

Random tumble pill tests by ASTM Method D-1375 show all three fabrics to have satisfactory pill resistance.

Example V A bicomponent fiber identical with Fiber A of Example IV is steamed after drawing then dried in a relaxed state. The tow is then cut on the Pacific converter to a varicut staple length ranging from 2.5 to 4.5 inches (6.35 to 11.43 cm.). Three ends of this sliver are combined with one end of Fiber B sliver processed on the Turbo stapler as in Example IV and the combined slivers are pin drafted to a final sliver weighing 70 grains per yard (5 grams per meter). This sliver is converted to 2/20s worsted count (88.6 tex.) yarn having a yarn shrinkage of 26%, and the latter knitted into a links and links pattern on an 8 cut Cal knitting machine. It is also knitted in a half cardigan stitch on a 7 cut Dubied machine and into a jersey fabric on a 12 cut Dubied machine.

Example VI A bicomponent fiber of 3.5 denier (0.39 tex.) is spun as in Example I. The spun fibers are washed and drawn 1.8x in water at 75 C. Tows of this fiber are combined with tows of Fiber B of Example I to give 75% of the bicomponent fiber and 25% of Fiber B. The combined tows are cut on the Pacific converter to out lengths of 3.5 to 5.5 inches (8.8 to 14 cm.) and then pin drafted and finally spun and plied into 2/ 30s Worsted count (59.2 tex.) yarn and knit into a full fashioned fabric. No holes appear in the fabric during 15 minutes of knitting. The fabrics are tested for pilling resistance by ASTM Method 1375 and found to be satisfactory. The fabric is bulky and soft with the good cover characteristic of the highly crimped bicomponent fibers. A fabric knit from 100% of the bicomponent fiber develops 14 holes when knit for 15 minutes.

Example VII A bicomponent fiber identical to that of Example V1 is combined at the Pacific converter with high shrinkage homofiber. The resulting sliver, in a ratio of 75% bicomponent fiber and 25 homofiber are further processed on finally converted to 2/ 30s worsted oount (59.2 tex.) yarns. This yarn knits for at least fifteen minutes with no holes appearing in the fabric and the resulting fabrics have good resistance to pilling as shown by ASTM Method D-1375.

This fabric is dyed to a uniform brown shade using the dyeing procedure of Example I and the following acid and cationic dyes:

Percent Acid Red 113 0.48 Acid Blue 25 (Color Index 62055) 0.133 Acid Yellow 17 (CI. 18965) 0.60 Basic Red 14 0.24 Basic Red 18 0.12

Percent Basacryl Blue GL 0.096 Basic Yellow 11 (CI. 48053) 0.45

The bicomponent fiber and the homofiber are found to be dyed to the same shade by this formula so that there is no two-tone effect.

It will be readily apparent that in preparing the homofibers for use as the high tenacity element in the yarns of this invention, alkyl vinyl pyridines and alkyl acrylates in general may be substituted for those specifically illustrated in the examples. Included among the other vinyl pyridines are 5 ethyl-Z-vinyl pyridine, 4,6-dimethyl-2- vinyl pyridine, 4-ethyl-2-vinyl pyridine and 6-methyl-2- vinyl pyridine. Among the additional alkyl acrylates are methyl and ethyl methacrylate, 2-nitro-2-methyl propyl methacrylate, methoxyethyl methacrylate, chloroethyl methacrylate, dimethyl aminoethyl methacrylate and the corresponding esters of acrylic and alpha-chloroacrylic acids.

What is claimed is:

1. A pill-resistant textile yarn prepared from a blend of two groups of acrylonitrile polymer fibers, the first group of fibers being low tenacity bicomponent fibers, each fiber comprising at least two fiber-forming acrylonitrile polymer compositions one of which contains from about 1% to 4.0% of copolymerized sodium styrene sulfonate in side-by-side relationship and being drawn from about 1.8 to about 2.1 times its original length and the second group of fibers being homofibers of substantially higher tenacity than those of said first group, each fiber of said second group of fibers comprising an acrylonitrile/alkyl vinyl pyridine/alkyl acrylate terpolymer and being drawn from about 3 to 6 times its original length, said yarn containing from about to of fibers of said first group and from about 10% to 30% of fibers of said second group.

2. The yarn of claim 1 wherein one component of said fibers of said first group is prepared from a blend of 90% polyacrylonitrile and 10% of a copolymer of 96% acrylonitrile and 4% sodium styrene sulfonate and the other component is prepared from a copolymer of 96% acrylonitrile and 4% sodium styrene sulfonate.

3. The yarn of claim 2 wherein the fibers of said second group are prepared from a terpolymer of acrylonitrile, methyl acrylate and Z-methyl-S-vinyl pyridine.

References Cited by the Examiner UNITED STATES PATENTS 3,039,171 6/1962 Hume et al 28-72 3,104,450 9/1963 Christens 57-140 3,128,527 4/1964 Schultz et al. 57 157 X FOREIGN PATENTS 870,017 6/1961 Great Britain.

FRANK J. COHEN, Primary Examiner.

J. PETRAKES, Assistant Examiner. 

1. A PILL-RESISTANT TEXTILE YARN PREPARED FROM A BLEND OF TWO GROUPS OF ACRYLONITRILE POLYMER FIBERS, THE FIRST GROUP OF FIBERS BEING LOW TENACITY BICOMPONENT FIBERS, EACH FIBER COMPRISING AT LEAST TWO FIBERS-FORMING ACRYLONITRILE POLYMER COMPOSITIONS ONE TO WHICH CONTAINS FROM ABOUT 1% TO 4.0% OF COPOLYMERIZED SODIUM STYRENE SULFONATE IN SIDE-BY-SIDE RELATIONSHIP BEING DRAWN FROM ABOUT 1.8 TO ABOUT 2.1 TIMES ITS ORIGINAL LENGTH AND THE SECOND GROUP OF FIBERS BEING HOMOFIBERS OF SUBSTANTIALLY HIGHER TENACITY THAN THOSE OF SAID FIRST GROUP, EACH FIBER OF SAID SECOND GROUP OF FIBERS COMPRISING IN ACRYLONITRILE/ALKYL VINYL PYRIDINE/ALKYL ACRYLATE TERPOLYMER AND BEING DRAWN FROM ABOUT 3 TO 6 TIMES ITS ORIGINAL LENGTH, SAID YARN CONTAINING FROM ABOUT 70% TO 90% OF FIBERS OF SAID FIRST GROUP AND FROM ABOUT 10% TO 30% OF FIBERS OF SAID SECOND GROUP. 